The non-obese diabetic (NOD) mouse provides an excellent model for e type 1 diabetes mellitus (T1DM). Several lines of evidence suggest that T1DM results from a Th1 autoimmune response. For example, studies by our group and others have shown that islet-reactive Th1 (interferon (IFN)-gamma producing) T cells transfer diabetes, while islet-reactive Th2 (interleukin (IL)-4 producing) T cells do not. These and other data support the notion that T1DM development correlates with a Th1 response. However, the pathogenesis of T1DM, like that of other organ-specific autoimmune diseases, clearly involves more than the development of IFN-gamma producing lymphocytes. Indeed, both IFN-gamma- and IFN-gamma receptor-deficient NOD mice develop T1DM. Therefore, it is critical that a deeper, more mechanistic understanding of the immunopathogenesis of T1DM be established. To this end, we have taken advantage of the spectrum of disease exhibited by sub-lines of our islet-specific T cell receptor (TCR) transgenic NOD mice to analyze the molecular evolution of disease in vivo, using the technique of functional genomics. The general hypotheses underlying these studies are: (a) that diabetes in NOD mice is a Th1-associated disease; (b) that disease expression in the NOD mouse is not dependent upon the expression or activity of IFN-gamma, the superficial phenotype marker of a Th1 response; and (c) that global characterization of disease- and tissue-specific gene expression will allow for a more complete understanding of the pathogenesis of diabetes in the NOD mouse. The specific hypothesis being tested in these studies is that a careful, functional genomics approach to molecular pathogenesis will allow for the detailed delineation of those aspects of the Th1-associated inflammatory response that are truly essential for disease pathogenesis in the NOD mouse. To this end, we aim: Aim 1: To establish a limited and verified set of genes whose expression patterns directly stage and predict the course of spontaneous disease progression in NOD mice. Aim 2: To delineate the genetic mechanism by which IFN-gamma- and IFN-gamma receptor-deficient NOD mice develop spontaneous T1DM in the absence of interferon-gamma activity. Aim 3: To establish the differential gene expression pattern associated with disease progression and resistance in NOD recipients of islet-reactive Th1 and Th2 T cells.